Question

A fluoride ion (F1-) has the same number of electrons as which of the following?

Answer 1

Answer : The correct option is, (d) $Mg^{+2}$

Explanation :

First we have to determine the number of electrons present in $F^{-1}$ ion.

Atomic number of fluorine (F) = 9

As we know that,

Atomic number = Number of electrons  (for neutral atom)

Number of electrons in $F^{-1}$ ion = 9 + 1 = 10

Now we have to determine the number of electrons present in given option ions.

For $B^{-3}$ ion:

Atomic number of boron (B) = 5

Number of electrons in $B^{-3}$ ion = 5 + 3 = 8

For $N^{+1}$ ion:

Atomic number of nitrogen (N) = 7

Number of electrons in $N^{+1}$ ion = 7 - 1 = 6

For $Na^{-1}$ ion:

Atomic number of sodium (Na) = 11

Number of electrons in $Na^{-1}$ ion = 11 + 1 = 12

For $Mg^{+2}$ ion:

Atomic number of magnesium (Mg) = 12

Number of electrons in $Mg^{+2}$ ion = 12 - 2 = 10

For $Ne^{-1}$ ion:

Atomic number of neon (Ne) = 10

Number of electrons in $Ne^{-1}$ ion = 10 + 1 = 11

From this we conclude that magnesium ion, $Mg^{+2}$ has the same number of electrons as a fluoride ion, $F^{-1}$.

Hence, the correct option is, (d) $Mg^{+2}$